Software Defined Networks (SDNs) and corresponding platforms are expected to be widely used in future generation networks and especially deployed and activated on-demand as agile networking control service components. The correct functioning of SDN platforms must be assured, i.e., such platforms should be thoroughly tested before deployment. After thorough verification of SDN controllers and switches, the composition of them still requires additional testing in order to guarantee the absence of critical faults. We propose a model based testing technique for checking SDN platforms that relies on appropriate graph enumeration. In particular, we define a fault model where the fault domain contains the wrongly and correctly implemented paths allowed with respect to the underlying resource connectivity graph. We also establish the conditions for deriving a complete test suite with respect to such fault model under black box and white box testing assumptions